`isOfferable` in `core/json/rootUnion.ts` checked that a merged branch carries
at least one property and that every property value is readable, but never that
each name in `required` resolves to a property a form can render. A branch like
`{ properties: { kind }, required: ["kind", "payload"] }` was therefore offered
in the picker, rendered no control for `payload`, and had the submit-time check
report it missing permanently — the exact dead end the function's own comment
already reasons through for a `false`-schema required field, one case short.
Judge the merge, so a branch requiring only names the ROOT declares —
`anyOf: [{ required: ["email"] }, …]` — stays offerable as before. `hasOwn`
rather than `in`, since an argument legally named `constructor` would otherwise
resolve through the prototype and read as declared.
Declining every branch of a union leaves the web form with neither a picker nor
a field, which is a different dead end. `SchemaForm` now seeds the raw-JSON
editor (#2151) in that one case — a root union that resolved to no branches and
no properties — so the arguments stay expressible. Seeded rather than forced, so
the switch still works, and re-seeded during render (never in an effect) because
the form is reused across tools rather than remounted. A tool that genuinely
takes no arguments is untouched. The TUI has no such editor; there the union is
simply not offered, which is already better than a section that can never be
submitted.
Adds a `record_shipment_by` preset and wires it into the
`root-union-schemas-http.json` showcase so the shape is reproducible by hand,
with docs/test-servers.md covering it.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01PxYT4eKdnx1yRw7x4bW7Ts
Signed-off-by: cliffhall <cliff@futurescale.com>
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